The present invention relates to integrated circuit (IC) memory devices and, more particularly, to the inclusion of one or more thin layers, such as Si, Al, IrO2, or Al plus TiN, as an adhesion layer between a noble metal layer, such as Pt, and a silicon dioxide (SiO2)layer to form the electrode for high-k dielectric Dynamic Random Access Memory (DRAM) and Ferroelectric Random Access Memory (FRAM) applications.
Capacitors with high dielectric constant (high-k) materials as the dielectric are increasingly used in high density devices. The high-k dielectrics used in DRAM devices are generally formed at a high temperature oxidation ambient, as are ferroelectric materials used in FRAM devices. To avoid oxidation of the electrodes at these high temperatures, noble metal electrodes are used with the dielectric. Platinum (Pt) electrodes are typically used for the high-k dielectric capacitors in DRAM devices and for FRAM devices because of its excellent oxidation resistance and high work function. However, Pt poorly adheres to silicon dioxide and results in peeling of the Pt at various process steps, such as during the formation of the capacitor and during the following Back End of Line (BEOL) processes. To prevent peeling, an intermediate adhesion layer may be added between the Pt and SiO2 layers. Currently, the adhesion layers used include Ti, TaSiN or TiN.
Though these materials can improve the adhesion between the Pt and SiO2 layers in the “as-deposited” state, roughening of the Pt surface or a local peeling has been observed after the subsequent annealing step which is typically at a temperature of 500 to 580° C. in an oxygen ambient. Further, when high-k dielectric and ferroelectric layers are deposited at temperatures below 500° C., the layers have degraded film quality with decreased capacitance, which degrades the performance of the device.
It is therefore desirable to provide an improved adhesion layer between the noble metal electrodes and the SiO2 layers. It is also desirable to provide an adhesion layer that prevents the peeling of the noble metal electrodes of the capacitor structures.